1. Field of the Invention
This invention relates to a device for introducing into the camera body side the information obtained by displacement of a movable member such as, for example, the aperture ring or the distance ring of a lens.
2. Description of the Prior Art
As the means for suitably quantizing a set value such as aperture, distance or the like of a lens and transmitting the same to a camera body, there is known one in which ON-OFF switches corresponding in number to the number of bits necessary for the transmission of the information are provided on the lens side and the connection between the camera body and the lens depends on an electrical connection by connecting terminals. However, such means involves much labor in the wiring work and in securing electrical reliability.
A photoelectric coupling system would occur to mind for the information transmission between the camera body and the lens. That is, the lens information is represented by a pattern provided on the lens and this is photoelectrically read. However, such system offers the following problem. Even for the same lens information, the output level of a photoelectric element is varied in accordance with the variation in brightness of the pattern illuminating light, so that it is difficult to detect the lens information from the output of the photoelectric element.